It could have been 1908. The Surrey Union hunt, all scarlets and dark blues in the crisp winter frost, was meeting for its traditional Boxing Day hunt at the Punchbowl Inn at Oakwoodhill. The master was atop a grey charger, 40 adults struggled to contain considerable steeds, and 60 well-spoken girls followed on their ponies as 1,000 or more hunt supporters munched greasy sausages and drank punch.

More than three years after hunting with dogs was banned, and contrary to predictions that the rural economy would collapse, hunting in Britain is as strong as it has been for years. Yesterday, said the Countryside Alliance, more than 300 hunts and 400,000 people were out.

But there are always some uninvited guests and just before midday at Oakwoodhill, 12 hunt saboteurs wearing traditional black, some carrying video recorders, piled out of a black Land Rover. Staying on the edge of the throng, they were barely noticed by the riders, but immediately attracted the attention of four policemen.

"It's deja vu," said Jo, one of the saboteurs. "We only come here to monitor the hunt and make sure it's legal, but we are endlessly harassed and photographed ourselves. We have caught this lot killing a fox twice this year and the police are more interested in us than taking them to court." That claim cannot verified, but hunt supporters make the point that it is not illegal to kill a fox - the law turns on the word "intent", and if a pack of dogs inadvertently gets a scent and goes on to kill a fox, well, that's just what dogs do.

"Nothing much has changed at all ..." agreed international events rider Pippa Funnell, before she spurred her horse down Honeywood Lane in pursuit of the master and the hounds. She was followed in turn by the saboteurs, the hunt followers and the police.

The Hunting Act, introduced in 2004, made it illegal to chase a wild animal with a pack of dogs except in certain circumstances, but independent monitors say fox hunts carry on as before, knowing that it is almost impossible to prove that people go out with the intention to hunt foxes as opposed to follow an artificial trail.

In three years, there have been only 31 prosecutions, mainly for hare coursing, and only three fox hunts have been taken to court. Neither hunters nor opposition groups are happy with the status quo.

"It's a ludicrous act ..." said Mark Sprake, a master of the Surrey Union hunt who thinks the law should be repealed. "It's not working. Far more foxes are being killed than before. The hunt used to keep a balance in the countryside but now gamekeepers are killing two to three hundred a year. It's created a nightmare situation."

Penny Little, of Protect our Wild Animals (Powa) which co-ordinates volunteer hunt monitors and presents video evidence of alleged lawbreaking to the police, wants the law strengthened: "Everyone knows there is wholesale lawbreaking going on. I have no hesitation in saying hunts are exploiting loopholes on a wide scale."

More than 60 MPs now want the ban to be strengthened. Meanwhile, the high court will shortly rule on whether hunts must prove that they are going out with no intention to chase foxes.

Yesterday, no foxes were killed by the Surrey Union. The hunters mainly treated the day as a public relations exercise and the heavily outnumbered saboteurs were content to watch. "[Law-breaking] happens well out of sight, mainly in the week when no one's around," said Little. "The hunts have found ways to avoid the law. They claim to be laying trails but surprise, surprise they lead directly to foxes. They go into the same covers and ditches, hedges and maize fields they always used to go to in the certainty that the fox will be there," said Little.

"We've given the Hunting Act a fair crack of the whip, but it's not stopping the killing," said Lee Moon, press officer with the Hunt Saboteurs Association. "They are putting foxes up left, right and centre and they are getting away with anything. The police are not interested."

The Countryside Alliance, which led the opposition to the law, yesterday called for its repeal. "People have got creative to keep within the law," said a source in the organisation who asked not to be named. "The fact is there is no way [hunts] are being policed. Hunts are aware there is the potential for prosecution so you would be silly to openly flaunt it. But 90% of the hunt don't even know what is going on during a hunt. You can do what you like. No one would know the difference between what is happening now and three years ago. There is effectively no difference."

Tim Bonner, a spokesman for the alliance, said: "There are videos of hounds chasing foxes, but if you take hounds into the countryside that's what they do. It's the intention of the huntsman, not the hound, that is crucial. There is no evidence that the hunt is outside the law."

Since the 2004 Act

• The Countryside Alliance says hunts are thriving since the change in the law, with more than 300,000 supporters

• No hunts have closed, or hunt workers been made redundant as a result

• There have been 31 prosecutions under the Hunting Act 2004, mainly for hare coursing; 15 cases are outstanding

• The Hunt Saboteurs Association says its numbers are on the rise as frustration mounts at police inaction

• Courts are confused about the law, and the high court will shortly rule on a definition of hunting. The government is under pressure to strengthen the law